As early as 2018, solar could be economically viable to power big cities. By 2040 over half of all electricity may be generated in the same place it's used. Centralised, coal-fired power is over

Last week, for the first time in memory, the wholesale price of electricity in Queensland fell into negative territory – in the middle of the day.

For several days the price, normally around $40-$50 a megawatt hour, hovered in and around zero. Prices were deflated throughout the week, largely because of the influence of one of the newest, biggest power stations in the state – rooftop solar...